This invention relates generally to solid ink printers and, more specifically, to drip plate surface features combined with melt plates for receiving solid phase change ink sticks. The solid phase change ink sticks are used in phase change ink color printers. The ink sticks are fed down feed chute slots to melt plates wherein the ink sticks are melted by the surface of drip plates and stored in a reservoir area in liquid form for ejection by a print head onto a receiving medium.
Solid ink jet printers were first offered commercially in the mid-1980""s. One of the first such printers was offered by Howtek Inc. and used pellets of colored cyan, yellow, magenta and black ink that were fed into shape coded openings that fed generally vertically into a heater assembly of a printer where they were melted into a liquid state for jetting onto a receiving medium. The pellets were fed generally vertically downwardly, using gravity feed, into the printer. These pellets were elongated and tapered on their ends and formed in different geometric shapes, each corresponding to a particular color.
Later more successful solid ink printers, such as the Tektronix Phaser.TM. III, the Tektronix Phaser.TM. 300, and the Jolt printer offered by Data Products Corporation, used differently shaped solid ink sticks that were either gravity fed or spring loaded into a feed chute and pressed against a heater or melt plate assembly to melt the solid ink into its liquid form. These ink sticks were shape coded and of a generally small size. One system utilized an ink stick loading system that initially feeds the ink sticks into a preload chamber and then loads the sticks into a load chamber by the action of a transfer lever. These ink stick feed systems melted the entire supply of ink, requiring all of the molten ink to be kept at an elevated temperature for extended periods of time to maintain the molten state, thereby tending to cause the molten ink to degrade over time from being maintained at the elevated temperature. Earlier solid or hot melt ink systems used a flexible web of hot melt ink that is incrementally unwound and advanced to a heater location or vibratory delivery of particulate hot melt ink to the melt chamber.
As phase change ink color printers have increased their printing speed, the need has developed to provide a greater ink capacity in the printer so replenishment is required less frequently and more output or prints can be produced between refills. In designs where there is not a steep or generally vertical feed path to the drip plate in the melt plate assembly, some provisions have been made to prevent the solid masses of shaped ink from sticking to the sides of the feed chute so that an unrestricted feed of ink sticks proceed into contact with the drip plate for melting and filling of the individual colored ink reservoirs that are usually located within the print head.
Ink sticks are placed into receptacles or openings in a cover plate over the feed chute slots. If an ink stick is inadvertently inserted through the wrong receptacle, it will result in incorrect image colors and can cause print head jetting problems. To prevent these problems, ink sticks and ink insertion openings are shaped or keyed to exclude all but the correct ink stick from being inserted. Therefore, an ink stick feed system has been provided that accommodates a plurality of ink sticks in an ink stick feed chute and efficiently feeds them into contact with melt plate assemblies that melt the ink and directs the molten flow into the individual colored ink reservoirs.
However, solid ink properties are being modified to produce a material that will improve auto document feed (ADF) performance. Media imaged with previous ink formulations would stick to various support and guiding surfaces, most notably glass, in almost all copy machines. The intentional soft, sticky nature of this ink enabled it to adhere to media and almost any other surface quite well. Newer ink with harder and more brittle characteristics improves ADF but presents new challenges since it does not stick as readily to most materials.
Manufacturing ink sticks with this newer material is more difficult because of its physical properties and the resulting product often has lots of invisible micro cracks and sometimes visible cracks, throughout the ink stick. Position control of the ink in the ink loader has become more difficult as the ink sticks do not tend to stick to one another sufficiently to keep the trailing end of an almost spent ink stick in place against the drip plate in a melt plate assembly. This allows portions of the ink stick at the crack lines to separate from the main body, where they can then slide off the drip plate as chunks or slivers during melting. These slivers do not always slide off the drip plate in a controlled fashion and they occasionally end up falling outside the intended printhead reservoir openings.
The melt front extending out from the face of an ink stick against the drip plate is large in area but quite thin. When the printer is exposed to shipping and handling shock and vibration, this thin, brittle material breaks free from the drip plate and falls off as xe2x80x9cchipsxe2x80x9d. The mass of the entire partially melted ink stick also easily breaks free from the drip plate surface, where it then bangs around and causes even more melt front chips to break free. Slivers of ink and solidified pools of ink where these chunks fall and melt similarly break free and join the chips in taking undesirable journeys throughout the printer. Some of this ink migrates outside the printer where it can rub and mark up the exterior to a very noticeable degree. It is possible for these ink particles to adversely affect printer operation (wedging between a drive belt and pulley or gear, as example).
Other printer improvements are being made along with the evolutionary changes to ink chemistry. Each new model prints at faster rates. This requires ink delivery to be faster as well. Given the limited speed with which thermal energy can be transferred into the ink, the best opportunity to increase melt rate performance is to increase the surface area of ink exposed to heated surfaces. This is problematic because the ink sticks cannot be made larger in existing architecture.
What is needed, therefore, is a simple and inexpensive ink delivery system that provides drip plate surface features for anchoring the ink stick and solidified melt front material, so that it remains affixed to the drip plate when solidified and also inhibits the unchecked sliding off of large separated slivers and chunks of ink during the melt and delivery operation. Additionally what is needed is greater heated surface area to transfer more thermal energy into the ink for faster melt rates by extending the heated portions of the drip plate into the ink stick. These needs are met by the apparatus of the present invention.
It is an aspect of the present invention to provide an improved ink stick feed system having an efficient and simple way of insuring a continuous supply of molten ink for printing by melting ink sticks against heated drip plates.
It is another advantage of the present invention to securely adhere solidified ink sticks to the drip plates such that the solidified ink stick does not come loose when exposed to shock or vibration.
It is another advantage of the present invention that the thin solidified ink melt front extending outwardly from the ink stick contact area on the drip plates is securely attached to the melt plate and does not come loose or chip when exposed to shock or vibration.
It is another advantage of the present invention that solid sections of ink which separate from the main block of an ink stick as it is consumed during melting are impeded from sliding off the melt plate as slivers or chunks and are instead fully or substantially melted.
It is yet another advantage of the present invention that features which impede the sliding off of slivers or chunks of melting ink direct such slivers and chunks toward the center of the drip plate where, if they are not fully melted, they slide in a more controlled fashion into the receiving reservoir.
It is a further advantage of the present invention to provide a greater heated surface area to which the ink is exposed on the surface of drip plates, thereby increasing the melt rate.
To achieve the foregoing and other aspects, features and advantages, and in accordance with the purposes of the present invention as described herein, a solid ink stick drip plate design is provided for a solid ink color printer which, in conjunction with the ink system load, feed and melt functions, reliably directs the on-demand ink flow and retains solidified ink.
The drip plates guide the molten ink into individual color ink reservoirs in the printer print head. The improved drip plate design includes a combination of one or more sized and shaped cutouts and protrusions for anchoring the solidified ink melt front and ink stick when the printer is not in operation and protrusions that impede downward movement of independent portions of a melting ink stick so that they remain in contact with the heated melt plate long enough to substantially melt, thereby inhibiting the unchecked sliding off of large separated slivers and chunks of ink during melt and delivery.
Still other aspects of the present invention will become apparent to those skilled in this art from the following description, wherein there is shown and described a preferred embodiment of this invention by way of illustration of one of the modes best suited to carry out the invention. The invention is capable of other different embodiments and its details are capable of modifications in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive. And now for a brief description of the drawings.